Research on group behavior has identified social loafing, i.e., the tendency of members to do less than their potential, as a particularly serious problem plaguing groups. Social Impact Theory (SIT) helps explain social loafing in terms of two theoretical dimensions--the dilution effect (where an individual feels submerged in the group) and the immediacy gap (where an individual feels isolated from the group). In this study, which employed a controlled experiment, we investigated these dimensions of social loafing in the context of group decision making, using collocated and distributed teams of varying sizes. Our results--in line with SIT--indicate that small groups, signifying a small dilution effect, had increased individual contributions and better group outcomes compared to their larger counterparts. However, support for SIT's arguments about the immediacy gap was mixed: Members contributed visibly more when they were collocated, but no significant differences in group outcomes were evident. Regardless of dimension, the quality of the input (ideas generated) determined the quality of the output (decisions made). Also, contrary to the literature on brainstorming, having more ideas to work with resulted in poorer-quality decisions. This apparent paradox is explained using the notion of integrative complexity, which challenges conventional wisdom regarding the relationship between individual inputs and group outputs. The implications of these results for practice and research are examined.